Rock-drill



W. A. SMITH.

ROCK DRILL.

APPLICATION FILED AUG.I3, 1920.

Patented July 112, 15921,

' warren stares rarest @FFHCE WILLIAM a SMITH, or r'nrtnrrsnune, new:rniasn'r, assrenoa 'ro INGERSOLL- renn n COMPANY, or JERSEY orrr, NEWanrsnr, A ooaroaarrou or NEW 7 JERSEY.

restate,

i ROCK-DRILL.

' Application filed August 13, 1920. Serial No. 403,354.

To all whom it may concern: 7

Be it known that T, WILLIAM A.SMITH, a citizen of the United States,anda resident of Phillipsburg, county of Warren, State of New Jersey,have invented certain new and useful Improvements in Rock -Drills, ofwhich the following is a specification. I

This invention relates to: a fluid actuated rock drill of the hammertype but more par:

ticularly to such a machine having a dilfer f ential double endedreversible piston provided with a main head, and shanks extending inopposite directions from said head and having reduced necks adjacent themain head. In this particular machine fluid pressure is intermittentlysupplied to and exhausted from'the larger bore of the cylinder in frpntof and behlnd the main head and also behind the rearwardlyextending'shank, so that a fluctuating pressure chamber is provided atthe rear or forwardly driving pressure surface of the said shank.

.The primary objects of the invention are to lengthen the back travel ofthe piston and produce. longer admission of fluid pressure against therear or forwardlydrivlngpressure surface of the main piston head on theThis is accomplished by forward stroke. means of a fluid actuatedd1fl'erent1alvalve controlling communication between adinission passagesleading respectively to a forward admission-port and another admlssiouuport located rearwardly of said forward admission port. In this instancethe valve is.

subjected to fluctuatingjpressure on one of its .difierential opposedoperative :surfaces tending to IIIOIVG the valve in a directionto opencommunication between said forward and rearward admission ports.v Inaccordance with this invention and as one of \its features, I providemeans for constantly subjecting another opposed differential pressuresurface of the valve to live air p essure tending to throw the valveover an and close communication between. the sa d forward.

and rearwardadmission ports.

Further objects of theinventi'on willhereinafter appear and to all ofthese ends the invention is shown in the accompanying drawings in one.of its preferred forms, in

j which- Figures 1 and 2 are diagrammatic longitudinalsectionalelevations of a .rock drill embodying the invention, showing the pistonhammer in two different positions.

Referring to the drawings, A represents the cylinder of a rock drillhaving the chuck B through which the drill steel C is inserted in theusual nuanner in position to receive the impact blows of the reversiblereclprocating hammer, which comprises the main piston head D having theforwardly and rearwardly extending reduced shanks E and F of the samediameter connected td the main head D by means of the necks G and H.

The main piston head D reciprocates in the larger bore J of the cylinderand the piston shanks E and F slide in bores of smaller diameter, theforward shank operated in the bore K and the rearward shank f operatedin the bore L of the back head, 0. The smaller boresK and L are of thesame diameter so that either shank may be inserted in either smallerbore to: make the piston reversible in case it is desired to so reverseit. Fluid pressure is supplied to the admission port P in the back headOthrough the inlet Q controlled by the usual throttle valve R and portsand passages are-provided in the cylinder and back head for distributingmotive fluid to and from the different portions of the cylinder. in thepresent instance the two forwardly driving pressure surfaces S and T andthe rearwardly driving pressure surface D are all intermittentlysupplied with pressure and the chamber V in the rearward portion of theback head U is thus a fluctuating pressure chamber to which pressure issupplied through the passage W communicating with the, rear portion ofthe main cylinder bope J, as indicated in dotted lines in the drawmgs.

j The main cylinder bore is provided withthe main exhaust port X andfluid pressure is supplied to the front end of the main cylinder bore infront of the piston head D through the passages Y and Z in the back headand cylinder respectively.

The supply of fluid pressure to the main cylinder bore behind the mainhead D is controlled partly by the valve a having a forward head 6 and'arearward head 0 connected by the reduced neck d and also providedvwiththe reduced shank or extension e. The smaller operative surface,- inthis I case the rearward surface f of the valve, is

subjected to constant pressure through the passage 9 communicating withthe supply passage h from the inlet Q. Another and larger opposedsurface j of the valve, in this instance the front end of the valvei'ssubjected to a fluctuating pressure through the passagehcommunicating with the main bore of the cylinder. The valve chamber 0is open to atmosphere atone point at ,the. port p. .v s

The forward admission'port 9 opens into the smaller bore in the backhead and conimunicates with the valve chamber 0 'by" means of theforward admission" passage '1. Another rearward admission passagescommunicates with the valve chamber 0 by means of the rearward admissionpassage t, which also communicates with the passage h.

In the operation of the machine let it be assumed that the piston is atthe forwardend of its stroke and 'is about to start on the back strokeas indicated in Fig. l. The main cylinder bore is shown exhaustingthrough the exhaust port X and therear fluctuating pressure chamber Vbehind the rearwardly extending piston shank F is also exhaustingasindicated by the arrows; Pressure is exhausted from in front of thepressure surface j of'the valve through the passage It and exhaust portX so that the constantpressure on the rearward surface f of the valvetends to hold the valve iii-its forward position as indicated in Fig,'1,

closing communication between the forward and rearward admissionpassages rand t.

The piston is ready for the rearward stroke and as it travels back, theexhaust port X to the back of the main head D is closed and 'thesupply'passage Z to the forwardend of the cylinder-is also closed by theforward piston extension E, but the shoulder to on v the rearwardextension F of the; piston overruns the forward admission port 9,without admitting pressure to the rear surface S of the' main head D,because the rearward adfull pressure be ind the main head-D missionpassage 25 is stillclosed by the valve 0. When the shoulder u on therearward extension of the piston over-runs the rearward 'admissionport sas indicated in Ei 2, pressure is admitted past the piston nec H to therear of the larger bore J of the cylinder, andfalso through passage K tothe front end j'of the valve '11, which throws the valv'eQto its-rearposition against the constant pressure exerted on the, smaller .surfacef of the valve and communication is opened-between the forwardand'rearward admission passa es 1" and 2? thus supplying 1 for drivingthe piston forward.

Owing to the fact that no pressureis sup-' plied to the rear ofthe-maincylinder head B when the forward admission port 9 is unsupplycovered by the piston shoulder a the piston has a substantially longrearward stroke 'beforethe forward and rearward admission passages r andt are placed in communication by the action of the valvea, and on theother hand, the piston is givena late cut-01f on" the forward stroke,because cut-off does not take place when the rearward admission port 8is over-run by the piston shoulder a but is delayed until the forwardadmissionport gis over-run by the'piston as indicated 4 in Fig. .1. Q

I claim: n 1; In a fluid operated rock drill of the hammer type, thecombination of a cylinder and reversible piston, means controlled by thepiston for supplying motive fluid to v the forward end of the cylinder,aforward' admission port and another admission port rearward of saidforward admission port for su plying motive fluid to the rearward end '0the cylinder, and a fluid actuated valve subjected to fluctuatingpressure on one operativesurface'and to constant pres-' sure onanopposed operative surface I for controlling communicationbetweenforward and rearward admission passages leading to ,said forward andrearward admission ports. 2. In afiuid operated rockdrill of the hammertype, thecombination of a cylin' der and reversible differential pistonsubject to fluctuating pressure on one of it's forwardly acting pressuresurfaces, means controlled by the pistonfor supplying motive fluid tothe rearw'ardly actmg pressure surf-ace of'the piston, a forwardadmission port and another admission port rearward; of said forwardadmission port for supplying motive to the other forwardl actingpressure surface of the pistonQan actuated valve subjected tofluctuating pres sure on' one operative surface and to con stantpressure on an opposedoperative surface for controlling communicationbetween forward and rearward admission passages leading to said forwardand rearward ad mission ports. 3

3. In a fluid operated rack drill; of the,

, hammer'type, the combination of a cylinder sages leading to saidforward and rearward admission ports, said valve being subject toconstant pressure on one operative sur- (face tending to closecommunication be-' tween said forward "and rearwardadmission,

passages and subject to fluctuating pressure on' an opposed operativesurface tending toopen communication between said forward and rearwardadmission passages.

4. In a fluid operated rock, drill of'the hammer t gpe, the. combinationof a cylinder and 'r versible difi'erential piston sub- 4 ject tofluctuatingpressure on one of its forwardly acting pressure surfaces,means co'ntrolled by'the piston for supplying .mo-

specification.

valve controlling communication between forward and rearward forward andrearward admission ports, said valvebeing subject to constant pressureon onefoperative surface tending to close communication betweenv saidforward and rearward admission passages, and Sub ect to fluctuatingpressure on an opposed operative surface tendlng to open communicationbetween said forward and rearward admission passages.

In testimony whereof I have signed this '.WILLIAM A. SMITH.-

admis'sion passages leading to said 1

